Both Hinduism and Buddhism teach that karma is the ironclad law of human existence: what goes around, comes around. Whatever moral energy you put out into the universe -- positive or negative -- you will then receive a corresponding reward or punishment. In Eastern thought, karma operates not only in this life, but even more powerfully in determining one's status in the next life.
As one definition explains: The process is automatic, and no interference by the gods is possible.
Karma, then, is inescapable. Think "you reap what you sow" on steroids.
Except, as U2 sings so artfully, grace "travels outside of karma." Whereas karma hems us in to an unavoidable law of cause & effect, grace in the end gives us better than we deserve. Grace is a gift that transcends our level of performance or accomplishment.
Grace, really, is what allows my level of blessing to be greater than my level of obedience.
When I end up with really good kids in spite of all my failures as a parent, my level of blessing is greater than my level of obedience.
When our church is strong in spite of my lackadaisical prayer life, my level of blessing is greater than my level of obedience.
When God sends people to support me in ministry even when I've not always been willing or able to mentor others, my level of blessing is greater than my level of obedience.
When I can celebrate a 25th wedding anniversary even though I've often been distracted or disengaged as a husband, my level of blessing is greater than my level of obedience.
When I can have assurance of my eternal salvation (I John 5:13) even when I'm painfully aware of the times I fail to love God with all my heart, my level of blessing is greater than my level of obedience.
All that is why there is no such song as "Amazing Karma."
I'll side with grace because I'm so grateful it sides with me.